New generations of low power, low cost, and portable sensing devices may be used in technologies related to homeland security, monitoring of agriculture, medical, and manufacturing environments, and other applications. For example, chemiresistors are chemical sensors based on a change in resistance in response to the binding of analytes and can be used for analyte detection, identification, and/or quantification. Chemiresistors generally have low power consumption and can give high precision resistance measurements. Typically, chemiresistors include a material capable of responding to a species (e.g., analyte). For example, several materials have been utilized as gas sensors, including metal oxides, organic semiconductors, and other materials. However, many of the current devices are limited by complex fabrication processes, high power consumption, and/or poor sensitivity. In some cases, organic materials have been considered as chemiresistor materials since molecular recognition elements may be readily integrated into their structures. However, such materials have been limited by electrostatic/dielectric interferences and fragile organic metal-interfaces.
Carbon-containing molecules such as graphite, carbon nanotubes, and fullerenes have attracted attention due to their unique mechanical and electronic properties, as well as their potential applications in nanotechnology. For example, carbon nanotube (CNT) field effect transistors have been studied as chemical and biological sensors. Their resistance can change drastically in the presence of analytes via, for example, charge transfer (e.g., doping), carrier pinning, and/or modification of the Schottky barrier at the carbon nanotube/metal contact. However, current applications have largely been limited by complexities associated with device fabrication.
Accordingly, improved devices and methods are needed.